ABSTRACT

The November 9, 1968 earthquake in south-central Illinois occurred in the
New Madrid zone, a seismic zone associated with northeast-trending geological
structure. Landforms in the epicentral area consist of nearly flat, glacial
lake plains surrounding low, loess-covered hills. An extensive post office
canvass and a field inspection of the epicentral area indicate that the
strongest shaking (MM VII) took place in the Wabash and Ohio Valleys and
adjacent lowlands of south-central Illinois. Characteristic damage included
broken chimneys, fallen plaster, and occasional instances of collapsed
parapets and overthrown tombstones. Observed rotations of tombstones and
other objects in the epicentral area suggest a quadrant distribution of
clockwise and counter-clockwise rotations.